(a) Field of the Invention
The present invention relates to a direct current (DC) power apparatus. More specifically, the present invention relates to a highly efficient DC power apparatus using a capacitor.
(b) Description of the Related Art
DC--DC converters convert a predetermined level of the DC voltage into another level of the DC voltage. The converter comprises a transformer including a first and a second winding wound on a magnetic core. By opening and closing a first circuit at a predetermined interval, the energy transfer between the first and the second windings can be controlled.
In the DC power apparatus industry, concerns for converters with small size, high energy efficiency, and high performance have recently increased. Also, slim portable devices using batteries are being developed as the technology develops.
FIG. 1 shows a conventional DC power apparatus using an inductor.
Referring to FIG. 1, an integrated circuit IC1 operating as a step-up DC power device boosts a battery voltage to a voltage required by a first terminal T1. A problem caused by this circuit is that the resisting pressure of the capacitor C1 must be greater than the voltage required by the first terminal T1.
Most devices supply the power to be used in the electronic circuits from the battery by using the step-down or step-up DC--DC converters. If the circuit being used requires a power greater than the battery voltage, the step-up converter must be used.
However, the DC power apparatus using this inductor generates noise, and in the case of wireless devices, these noises greatly lower the performance of the apparatus. In the case of using a power greater than the battery voltage and needing much current, the performance of the DC power apparatus greatly varies according to the amount of the current used. In the case of the portable devices, these kinds of circuits are in standby mode most of the time when in use, and the efficiency at this time becomes much lower.
In a conventional boost circuit using an inductor, frequency spectra caused by switching noises affect the operation of radio frequency (RF) or intermediate frequency (IF) parts. Since the boost circuit uses a method whereby it is connected to the battery in parallel, a voltage as high as the desired output voltage is needed.
Also, because the conventional method uses a switching method using an inductor, the conversion efficiency greatly varies depending to the output current.